Circuit interrupter embodying 2, 4 dichloro benzoic acid or 3, 4 dichloro benzoic aci



H. H. FAHNOE 3,184,568

2 Shets-Sheet 1 D7//////////Hfll/Y//////Y///ZI/IZIAV/l/l/JA ASH,

INVENTOR. HAROLD H. FAHNOE MOVEMENT OF LOWER END OF ROD LIKE TERMINALditty.

May 18, 1965 CIRCUIT INTERRUPTER EMBODYING 2,4 DICHLORO BENZOIC v ACIDOR 3,4 DIGHLORO BENZOIC ACID Filed 001:. l, 1962 v y 1965 H. H. FAHNOE 13,184,568

CIRCUIT INTERRUPTER EMBODYING 2 ICHL BENZOIC ACID on 3,4 are HLORO BE ISA Filed Oct. 1, 1962 2 SheetsSheet 2 ADHESIVE WRAPPER DICHLOR BENZOICACID OR A MIXTURE THEREOF.

BORIC ACID United States Patent CIRCUIT INTERRUPTER EMBODYTNG 2,4 Dl-CHLORO BENZUIC A811) @R 3,4 DEQHLQRG BENZUIQ ACID Harold H. Fahnoe,Evanston, 111., assignor to S. 81 C. Electric Company, Chicago, Tlh, acorporation of Delaware Filed Oct. 1, 1962, Ser. No. 227,325 11 Claims.(Cl. 260-420) This invention relates, generally, to circuit interruptersand it has particular relation to are extinguishing means in circuitinterrupters for use on alternating current transmission circuitsoperating at voltages of the order of 34.5 kv. and above.

It is conventional to draw an arc in a bore formed in a stack of cakesof boric acid from which an arc extinguishing medium in a vapor orgaseous form is evolved that assists in extinguishing the arc. There isan optimum relation between the diameter of the bore and the currentflow that can be interrupted efiiciently therein at a given voltagewhile leaving the surface of the bore after arc extinction capable ofwithstanding the open circuit and transient voltages that may be appliedso that the arc will not restrike. The larger the diameter of the borethe greater will be the ability of the circuit interrupter to interruptcurrent flow and extinguish the arc incident thereto. However, when thedevice is required to interrupt a substantially smaller current flow inthe same material and the same bore, the operation is much lessefiicient.

Accordingly, among the objects of this invention are: To improve theoperating characteristics of a circuit interrupter of the solid materialtype provided with a bore in which the arc is drawn and extinguished,particularly for the lower current ranges while utilizing its inherentelliciency for the interruption of current flows in the higher currentranges; to form a continuation of the high current interrupting bore insolid arc extinguishing material at the same diameter which continuationinherently is capable of assisting in the efficient interruption ofrelatively low current flow and is much less efiicient in assisting inthe interruption of the relatively high current flow; to form the arcextinguishing materials into stacks of apertured cakes in endwiserelation and to cement them in place inside a tubular insulating housingwith the apertures in the cakes forming a bore through which a rod liketerminal moves to draw the arc therein; and to pre vent the cement fromhaving direct contact with the stack of cakes of arc extinguishingmaterial that are adapted particularly for the eflicient interruption ofrelatively low current flows or the flow of relatively low faultcurrents.

' In the drawings:

FIGS. 1A, 1B and 1C placed one above the other in the order named show acircuit interrupter of the solid material fuse type in which thisinvention is embodied, the construction being a vertical longitudinalsectional view of such a fuse.

FIG. 2 is a vertical sectional view, at an enlarged scale, of asub-assembly for the arc extinguishing material that is capableinherently of assisting in the extinction of relatively low currentarcs.

FIG. 3 is a horizontal sectional view, at an enlarged scale, takengenerally along the line 22 of FIG. 1B.

Referring now particularly to FIGS. 1A, 1B and of the drawings, it willbe observed that the reference character 11} designates, generally, acircuit interrupter of the solid material type that is intended to bepivotally mounted at its lower end and to be latched at its upper end.The circuit interrupter 10 can be employed in a dropout fuse mountingconstructed as shown in US. Patout No. 2,578,255, issued December 11,1951, to S. l.

3,184,568 Patented May 18, 1965 Lindell. Also it can be employed in thedropout fuse construction shown in US. Patent No. 2,651,695, issuedSeptember 8, 1953, to C. H. Baker. It can be employed without thedropout features in a non-dropout solid material type of fuseconstruction such as shown in US. Patent No. 2,961,514, issued November22, 1960, to S. I. Lindell. More specifically it can be employed in thedropout fuse construction shown in copending application Serial No.232,845 filed October 24, 1962 in the name of Henry J. Barta andassigned to the assignee of this application.

The circuit interrupter 1d includes a tubular housing 11 of insulatingmateiral that is weatherproof and has substantial strength. For example,the tubular housing 11 can be formed of a phenolic condensation productor like material. At its upper end it is provided with an upper tubularterminal 12 which is telescoped inside of the upper end. At its lowerend the tubular housing 11 has a lower terminal 13 in the form of aferrule telescoped over the outer surface thereof.

The upper end 14 of the tubular terminal 12 is inwardly flanged tooverlie a washer 15 having a central opening 16 through which a latchtrip pin 17 can project for tripping the latch mechanism of the fusemounting to release the circuit interrupter 1t and permit it to swingdownwardly in conventional manner for providing an air gap in thecircuit.

The latch trip pin 17 constitutes an upward extension from a rod liketerminal 18 which is provided at its upper end with a rod end fitting 19having a downwardly facing shoulder 20 against which the upper end of acoil compression spring 21 reacts. The lower end of the coil compressionspring 21 bears against an inclined shoulder 22 that is located near thelower end 23 of the tubular terminal 12. It is secured by rivets 24 tothe lower end of a contact sleeve 25. The contact sleeve 25 includesupwardly extending contact fingers 26 which are urged inwardly by agarter spring 27 into contact engagement with a contact section 23 ofthe rod like terminal 18. it will be understood that this constructionprovides a simple and efficient means for making a low resistanceconnection between the tubular terminal 12 and the rod like terminal 13.When the rod like terminal is released for upward movement under theinfluence of the coil compression spring 21, the circuit is completedfrom the contact fingers 26 to the smaller diameter portion of the rodlike terminal 18 below the contact section 28 for the short time duringwhich the rod like terminal 18 moves upwardly to effect circuitinterruption.

The rod like terminal 18 is restrained from upward movement under theinfluence of the coil compression spring 21 by a fusible element that isindicated, generally, at 31. The fusible element 31 is connected to aterminal rod 32 which is stationarily mounted at the lower end of thetubular housing 18. The fusible element 31 preferably includes a fusewire 33, that may be formed of silver, and a strain wire 34 that may beformed of nickel chromium alloy wire. The fuse and strain wires 33 and3d are suitably secured in the respective end of the rod like terminal13 and the terminal rod 32 by deformation of the latter onto the former.The terminal rod 32 extends through and is anchored to a transverselydisposed bridge 35 by nuts Bid-36. The bridge 35 is mounted on an innermetallic sleeve 37 which extends upwardly through the lower end of thetubular housing 11 with its lower end 38 being secured by rivets 39 tothe lower end of the lower terminal 13. The exhaust lower end of thetubular housing 11 is closed by a disc 4-0 of suitable insulatingmaterial which can be readily ruptured or blown out as the result ofpressure generated in the inner metallic sleeve or exhaust tube 37occasioned by the blowing of the fusible element 31.

The rod like terminal 18 extends downwardly from the contact section 28through a cup shaped end washer 43 and through a bore 44 that is formedby the apertures in a stack of cakes of arc extinguishing material to bedescribed.

The upper end of the bore 44 extends through a subassembly that isindicated, generally, at 45 and is shown in detail in FIG. 2. As hereshown, the sub-assembly 45 includes an upper end cake 46 f boric acid.Below the upper end cake 46 of boric acid there is a stack of cakes 47that are formed of 2,4-dichloro benzoic acid or 3,4-dichloro benzoicacid or a mixture of equal parts of these materials. The extinguishingability of that portion of the bore 44 extending through the cakes 4'7is exceptionally eflicient for assisting in interrupting relatively lowcurrent arcs but, due to the deposition of carbon over the surface ofthe bore 44 after arc extinction, they are not as efficient as boricacid for the interruption of high current arcs. At the lower end of thestack of cakes 47 there is a cake 48 of boric acid through which thebore 44 extends. The lower end cake 48 of boric acid and the upper endcake 46 provide terminal sections for the sub-assembly 45 with the cakes47 of 2,4-dichloro benzoic acid or 3,4- dichloro benzoic acid or amixture of equal parts thereof interposed therebetween with the bore 44extending entirely therethrough for receipt of the rod like terminal 18.Overlying these cakes in stacked relation is an adhesive wrapper 49. Itmay be formed of suitable pressure sensitive insulating material whichnot only maintains the cakes 46, 47 and 48 in the stacked relationshipbut also it prevents a self setting epoxy cement, to be described, fromcontacting the exterior surfaces of the cakes 47, a condition that isnot conducive to the proper curing of the self setting epoxy cement.

As shown in FIGS. 13 and 10, the bore 44 continues through a stack ofcakes 50 of boric acid that are located below the sub-assembly 45. Thelowermost cake 50 is provided with a conical throat 51 into which thearc is first drawn on blowing of the fusible element 31. Below thelowermost cake 50 is a fiber plug 52 that defines an arcing chamber 53in which the principal portion of the fusible element 31 is positionedand in which the are initially is drawn.

The assembly of the sub-assembly 45 and the cakes 50 of boric acid inthe tubular housing 11 is carried out generally in accordance with theteaching of U.S. Patent No. 2,961,514, issued November 22, 1960, to S.I. Lindell. The assembly as shown in FIGS. 1A, 1B and 1C is made withoutapplication of the lower terminal 13 and with the rod like terminal 18,coil compression spring 21, fusible element 31 and terminal rod 32omitted. The arrangement is such, as shown here, that a slight space isprovided between the several parts and the inner surface of the tubularhousing 11. This space is filled with a self setting cement which isindicated at 54 in FIG. 3. Preferably, as indicated in the patent lastmentioned, the cement 54 is an epoxy resin. After the cement 54 hassuitably cured, the remaining assembly is made of the various parts tocomplete the circuit interrupter 10.

In operation, upon blowing of the fusible element 31 as the result ofthe flow therethrough of a relatively high fault current, the rod liketerminal 18 is released and it is moved upwardly under the influence ofthe coil compression spring 21. The are is drawn between the upper endof the terminal rod 32 and the retreating lower end of the rod liketerminal 18 first in the arcing chamber 53 and then it is extended intothe lower end of the bore 44 in the cakes 50 of boric acid. Here thelarge current arc is efficiently extinguished as the result of theevolution of an arc extinguishing medium in vapor form from the surfaceof the bore 44. Within the interrupting capability of the circuitinterrupter 10, the large current are will be extinguished before thelower end of the rod like terminal 18 is moved past the uppermost cake50 of boric acid. However, the construction is such that the lower endof the rod like terminal 18 can be moved to a final position that isindicated by broken line 55, FIG. 13, which extends through the uppercake 46 of boric acid at the upper end of the sub-assembly 45.

In the event that the current flow through the fusible element 31, whilesufficient to cause it to blow, is of a relatively small magnitude, thearc tends to persist while the lower end of the rod like terminal 18 isbeing drawn entirely through that portion of the bore 44 in the cakes 50of boric acid and is extended into that portion of the bore 44 thatextends through the cakes 47 that are formed of 2,4-dichloro benzoicacid or 3,4-dichloro benzoic acid or a mixture of these materials. Herethe relatively low current are is extinguished in the bore 44 which hasthe same diameter throughout the several cakes 46, 47, 48 and 58 of arcextinguishing material.

As pointed out above, the circuit interrupter 10 employing thesub-assembly 45 is capable of interrupting relatively low fault currentsas well as fault currents of much higher magnitude. To demonstrate thiswide range of current interrupting ability 2. test was made using cakesof boric acid, such as the cakes 59, in a number such as to provide alength of nineteen inches. While this construction was capable ofinterrupting relatively high fault current, it was not capable ofclearing fault currents of a mag nitude below amperes. For comparisonpurposes a comparable construction was made in which the subassembly 45comprised cakes 46 and 47 of boric acid each having a length of one inchand located at the ends of cakes 47 of 2,4-dichloro benzoic acid havinga length of five inches in combination with cakes 50 of boric acidhaving a length of twelve inches, the total length being nineteeninches. The circuit interrupter 10, using this arrangement of arcextinguishing materials, readily cleared fault currents down to theminimum melting current of ten amperes of the smallest fusible element31 that was used. In addition this arrangement was capable of clearingall higher values of fault current of the order of those cleared by theconstruction using boric acid cakes alone. In order that a propercomparison of operating characteristics could be made the tests justreferred to were conducted under identical conditions of availablerecovery voltage and available rate of rise of recovery voltage at thetime of fuse clearing.

What is claimed as new is:

1. An electric circuit interrupter comprising, in com bination:

(a) means between which an arc is formed on interruption of the circuit,and

(b) means adapted to confine and extinguish said are disposed along thepath thereof from which an arc extinguishing medium can be evolved dueto the heat of said are for extinguishing it, the last named means beingselected from the class consisting of 2,4-dichloro benzoic acid and3,4-dichloro benzoic acid.

2. The invention, as set forth in claim 1, wherein the arc confining andextinguishing means comprises a mixture of 2,4-dichloro benzoic acid and3,4-dichloro benzoic acid.

3. A sub-assembly for use in a circuit interrupter, in combination,

(a) a stack of cakes of arc extinguishing material selected from theclass consisting of 2,4dichloro benzoic acid and 3,4-dichloro benzoicacid having a bore extending therethrough,

(b) a cake of boric acid at each end of said stack having an openingtherethrough to provide continuations of said bore, and

(c) an adhesive wrapper impervious to epoxy resin surrounding said cakesand holding them in endwise assembled relation.

4. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore in which an arc is drawn andextinguished,

(b) means for drawing the are into said bore at one end,

(c) a first solid arc extinguishing material comprising boric acid insaid housing defining said bore at said one end and characterized bybeing effective for the interruption of relatively high current arcs andsubstantially less effective for the interruption of rela tively lowcurrent arcs, and

(d) a second solid arc extinguishing material selected from the classconsisting of 2,4-dichloro benzoic acid and 3,4-dichloro benzoic acid insaid housing and defining a continuation of said bore and characterizedby being effective for the interruption of relatively low current arcsand substantially less effective for the interruption of relatively highcurrent arcs.

5. The invention, as set forth in claim 4, wherein the means for drawingthe are into the bore is a rod like terminal that is shifted as a partof a continuous movement through the bore in the first solid arcextinguishing material and then through the bore in the second areextinguishing material.

6. The invention, as set forth in claim 5, wherein:

(a) the first solid arc extinguishing material comprises a stack ofapertured cakes in spaced relation to the inner surface of the tubularhousing,

(5) the second solid are extinguishing material cornprises a stack ofapertured cakes in spaced relation to said inner surface of said tubularhousing, and

(c) an adhesive means fills the space between said cakes and said innersurface of said tubular housing and secures them together as an integralunit.

7. The invention, as set forth in claim 6, wherein:

(a) the adhesive means is an epoxy resin, and

(b) a layer of insulating material impervious to epoxy resin overliesthe stack of cakes forming the second solid arc extinguishing materialand prevents direct contact therebetween.

8. The invention, as set forth in claim 6, wherein an apertured cake ofthe first solid are extinguishing material provides a continuation ofthe bore at the end remote from the end where the are is drawn andwithin which the are drawing end of the rod like terminal is located atthe end of its movement.

9. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore of substantially uniform diameterin which an arc is drawn and extinguished,

(b) means for drawing the arc into said bore at one end,

(c) a first solid arc extinguishing material in said housing definingone section of said bore at said one end and characterized by beingparticularly effective for the interruption of relatively high currentarcs, and

(ci) a second solid arc extinguishing material in said housing differentfrom said first solid arc extinguishing material and defining anothersection of said bore remote from said one end and having the samediameter as that of said one section thereof adjacent thereto andcharacterized by being exceptionally etficient for the interruption ofrelatively low current arcs and substantially less efficient for theinterruption of relatively high current arcs.

10. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore of substantially uniform diameterin which an arc is drawn and extinguished,

(b) means for drawing the are into said bore including a stationaryterminal at one end thereof and a rod like terminal that is shifted as apart of a continuous movement through said bore and substantiallyfilling the same,

(0) a first solid arc extinguishing material in said housing definingsaid bore at said one end and characterized by being particularlyeffective for the interruption of relatively high current arcs, and

(d) a second solid arc extinguishing material in said housing differentfrom said first solid arc extinguishing material and defining acontinuation of said bore of the same diameter and characterized bybeing exceptionally efiicient for the interruption of relatively lowcurrent arcs and substantially less efiicient for the interruption ofrelatively high current arcs.

11. An electric circuit interrupter comprising, in combination:

(a) a tubular housing providing a bore of substantially uniform diameterin which an arc is drawn and extinguished,

(b) means for drawing the are into said bore including a stationaryterminal at one end thereof and a rod like terminal that is shifted as apart of a continuous movement through said bore and substantiallyfilling the same,

(c) a first solid arc extinguishing material in said housing definingsaid bore at said one end and characterized by being particularlyeifective for the interruption of relatively high current arcs,

(d) a second solid arc extinguishing material in said housing differentfrom said first solid arc extinguishing material and defining acontinuation of said bore of the same diameter and characterized bybeing exceptionally efficient for the interruption of relatively lowcurrent arcs and substantially less efiicient for the interruption ofrelatively high current arcs, and

(e) a solid arc extinguishing material in said housing defining acontinuation of said bore in said second solid are extinguishingmaterial and formed of said first solid arc extinguishing material andwithin which the are drawing end of said rod like terminal is located atthe end of its movement.

References Cited by the Examiner UNITED STATES PATENTS 2,531,007 11/50Strom et a1. 200--l4-9 2,577,899 12/51 Linton 200135 2,752,458 6/56Baker et a1 200- 2,913,49 11/59 Dazzi 252-63.2 2,976,381 3/61 Lindell200-420 BERNARD A. GlLHl-EANY, Primary Examiner.

1. AN ELECTRIC CIRCUIT INTERRUPTER COMPRISING IN COM BINATION: (A) MEANSBETWEEN WHICH AN ARC IS FORMED ON INTERRUPTION OF THE CIRCUIT, AND (B)MEANS ADAPTED TO CONFINE AND EXTINGUISH SAID ARC DISPOSED ALONG THE PATHTHEREOF FROM WHICH AN ARC EXTINGUISHING MEDIUM CAN BE EVOLVED DUE TO THEHEAT OF SAID ARC FOR EXTINGUISHING IT, THE LAST NAMED MEANS BEINGSELECTED FROM THE CLASS CONSISTING OF 2,4-DICHLORO BENZOIC ACID AND3,4-DICHLORO BENZOIC ACID.